Project Summary Systemic sclerosis (SSc) is a systemic autoimmune disease that results in widespread fibrosis of the skin and internal organs, vascular dropout and autoantibody formation. SSc has the highest case fatality rate of any systemic autoimmune disease and there remain no FDA-approved therapies. Our data and that of others indicate that the innate immune system is the major driver of fibrosis in SSc. Analysis of gene expression data on samples collected from SSc patients strongly indicates that alternatively activated macrophages are key drivers of SSc pathogenesis. The scientific premise of our approach is that the innate immune system, primarily alternatively activated macrophages (Ms), is a key driver of SSc across multiple end-target organs and the elimination of such Ms will result in decreased fibrosis. To address this, we designed a novel therapeutic approach to eliminate alternatively activated Ms. In Phase I studies, we demonstrated that targeted elimination of a subpopulation of Ms using chimeric antigen receptor (CAR) T cells led to a reduction in skin thickness in a bleomycin mouse model of skin fibrosis. Moreover, removal of these cells during the development of fibrosis resulted in an overall reduction of gene expression associated with progression of the disease. Our goal in Phase II is to further develop a cellular therapy that targets alternatively activated macrophages through the use of chimeric antigen receptor (CAR) T cells and our lead targeting construct developed in Phase I. We demonstrated that CAR T cells ameliorated the fibrotic process locally, and anticipate the same impact systemically. By the end of Phase II, we will have performed the required IND-enabling studies to move this therapeutic approach into the clinic. The specific aims of this Phase II grant application are: 1) Demonstrate the therapeutic efficacy of CAR T cells in SSc models; 2) Create human CAR T cells against SSc Ms and optimize manufacturing production; and 3) Determine anti-CD206 CAR T cell persistence in vivo using a systemic model of fibrosis.